An aspect of the invention relates to a method of matching analog communications lines in telecommunications networks, whereby signal processors and/or programmable digital filters are used. Further, the invention comprises a device for executing the procedure as well as a program product.
To implement digital four-wire connections on analog two-wire access lines, what are known as codecs or coder/decoder filters with converters to convert analog to digital and vice versa are used on subscriber and exchange modules together with the Subscriber Line Interface Circuits. The lines are matched to country-specific line parameters, for example, by programmable digital filters for which the parameter set is adapted to the relevant line parameter. The parameter set is based on data which is specified by a provider, a network operator or a telecommunications authority for a standard network case. Meaning, individual lines, depending on the quality and features of the network, can differ to a greater or lesser extent since connected lines can exhibit different impedance from each other based on qualitative and quantitative differences in line interfaces, which leads to incorrect line matching. In particular, in interfaces between internet protocol-based networks, known as “Voice-Over-IP” networks and networks known as PTSN (“Public Switched Telephone Network”). For example, known telephone networks with analog exchange lines the incorrect line matching results in reflections at the 4-wire to 2-wire conversion, which as a result of the high delay of the IP networks in comparison to PSTN is only audible in PSTN-IP network couplings as an acoustic echo. The additional fault locations defined by the incorrect matching result in greater computing effort and increased calculation effort for the echo compensators, used between the PSTN and IP network in order to reduce the echo for the input-side line. In particular, at the beginning of a communications link, the effect caused by the additional fault location leads to an audible echo. Because of the increased computation time and the correspondingly slow convergence behavior of the echo compensators used, the execution sequence for this type of communications link remains adversely affected in this state of-the-art.
By contrast, One object of the invention is to provide a method mentioned at the start of this document with which incorrect line matching and the resulting reflections, in particular, for transmission gateways from Internet Protocol-based networks or mobile radio networks to analog telephone networks are largely minimized in a cost-effective way. And, the line-specific (constant for each access line) (residual) matching can again be fed back from the echo compensator, which should only compensate for connection-specific echoes as quickly as possible, to the line circuit.